Inertial navigation units are essential location and attitude sensors employed in practically all aerospace vehicle platforms. Fiber optic versions deployed in recent years offer greater sensitivity and reliability than the early mechanical devices. The all-fiber optical gyroscope was first proposed in 1980 as an implementation of a Sagnac phase shift interferometric inertial rotation sensor. The all-fiber guided wave approach yielded a compact, simplified and more stable version than the bulk optical approach of the prior art. In 1981, the use of a low coherence length light source was proposed to mitigate excess phase noise errors resulting from Rayleigh backscattered light generated in the optical gyroscope's long fiber sensing coil.
The first low coherence source considered for fiber optic gyroscopes was a superluminescent diode with a broad emission spectrum. These devices while very compact have limited applicability due to the large temperature coefficient of their average emission wavelength. Erbium-doped superfluorescent fiber sources were later adopted as the broadband light source of choice for the most sensitive fiber optic gyroscopes on account of the higher output power and better than 100× reduction in the temperature coefficient of their average emission wavelength to values below 5 ppm per ° C.
There is a need for a compact, lightweight, robust and/or low cost broadband light source.